BIO152H5 Chapter Notes - Chapter 7: Microfilament, Nuclear Membrane, Pinocytosis

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CHAPTER 7: INSIDE THE CELL (PGS. 125-156)
Key Concepts
- The structure of cell components is closely related to their function.
- Inside cells, materials are transported to their destinations with the help of molecular “zip
codes” or postal codes.
- Cells are dynamic. Thousands of chemical reactions occur each second within cells;
molecules constantly enter and exit across the plasma membrane; cell products are shipped
along protein fibres; and elements of the cell’s internal skeleton grow and shrink.
Introduction
- Life on earth is cellular
7.1 What’s Inside the Cell?
- Looking at cell structure, there are two broad groupings of life:
- Prokaryotes, which lack a membrane-bound nucleus.
- Eukaryotes, which have such a nucleus.
- Looking into groupings by evolutionary history, there are two types of prokaryotic cells,
called Bacteria and Archaea, in addition to the Eukarya.
Prokaryotic Cells
- The prokaryotic plasma membrane surrounds the cytoplasm, a term that includes all the
contents of the cell.
- Most prokaryotic species have one supercoiled circular chromosome containing DNA that is
found in the nucleoid region of the cell.
- All prokaryotic cells contain ribosomes for protein synthesis. Ribosomes have a large and a
small subunit and contain both RNA and protein molecules.
- The inside of prokaryotic cells is supported by a cytoskeleton of protein filaments.
- Some prokaryotes have tail-like flagella on the cell surface that spin around to move the
cell.
- Prokaryotic cells generally have few or no substructures separated from the rest of the cell
by internal membranes.
- Prokaryotes have a tough cell wall that protects the cells and gives them shape and
structure.
Eukaryotic Cells
- The relatively large size of the eukaryotic cell makes it difficult for molecules to diffuse
across the entire cell. This problem is partially solved by breaking up the large cell volume
into several smaller membrane-bound organelles.
- The compartmentalization of eukaryotic cells increases chemical reaction efficiency by
separating incompatible chemical reactions and grouping enzymes and substrates together.
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Notes From Reading
CHAPTER 7: INSIDE THE CELL (PGS. 125-156)
Eukaryotes and Prokaryotes Compared
- Major differences between typical eukaryotes and prokaryotes are as follows:
(1) Eukaryotic chromosomes are found inside a membrane- bound compartment called a
nucleus.
(2) Eukaryotic cells are often much larger.
(3) Eukaryotic cells contain extensive amounts of internal membrane.
(4) Eukaryotic cells feature a diverse and dynamic cytoskeleton.
Location of DNA
Internal
Membranes and
Organelles
Cytoskeleton
Overall Size
Bacteria and
Archaea
In nucleoid (not
membrane
bound); plasmids
also common
Extensive internal
membranes only
in photosynthetic
species; limited
types and
numbers of
organelles
Limited in extent,
relative to
eukaryotes
Usually small
relative to
eukaryotes
Eukaryotes
Inside nucleus
(membrane
bound); plasmids
extremely rare
Large numbers of
organelles; many
types of organelles
Extensive usually
found throughout
volume of cell
Most are larger
than prokaryotes
The Nucleus
- All eukaryotes have a large nucleus surrounded by a double-membrane nuclear envelope.
The nucleus contains the linear eukaryotic chromosomes.
- Ribosomal RNA synthesis occurs in a distinct region of the nucleus called the nucleolus.
Ribosomes
- Eukaryotic ribosomes are made of RNA and protein, and have a large and a small subunit.
Many ribosomes are found in the cytosol, the fluid part of the cytoplasm.
Rough Endoplasmic Reticulum
- The rough endoplasmic reticulum (rough ER) is a network of membrane-bound tubes and
sacs studded with ribosomes for protein synthesis and is continuous with the nuclear
envelope.
Golgi Apparatus
- The Golgi apparatus is formed by a series of stacked flat membranous sacs called cisternae.
It receives products from the rough ER and sends finished products to the cell surface in
vesicles.
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